Generally, an axial direction discharge valve assembly among valve assemblies of a general reciprocating compressor is a device in which a piston installed as a single body with an armature of a motor undergoes a linear reciprocating movement inside a cylinder, sucks a refrigerant gas, and compresses and discharges the refrigerant gas to moving direction of the opened/closed when the piston undergoes the reciprocating movement is closely related to a function of the entire discharge valve assembly.
FIGS. 1 and 2 are a perspective view and a longitudinal cross-sectional view showing an embodiment of the axial discharge valve assembly (hereinafter, referred to as discharge valve assembly) described above.
As shown therein, in the conventional discharge valve assembly, a piston 1 integrated with an armature (not shown) of a motor is inserted into a cylinder 2, and undergoes a linear reciprocating movement. And the discharge valve assembly comprises: a discharge cover 3 fixedly coupled to front end surface of the cylinder 2 for forming a certain discharge space S2; a discharge valve 4 of hemisphere shape which is installed in the discharge cover 3 for controlling the discharge of the compressed gas by opening/closing the cylinder 2 as contacted/separated to/from the front end surface of the cylinder 2 in the discharge cover 3 while the reciprocating movement of the piston 1; and a valve spring 5 supported between the discharge cover 3 and the discharge valve 4 for elastically supporting the reciprocating movement of the discharge valve 3.
The valve spring 5 is a cylindrical compressed coil spring wound so as to have same spring constant and same rotation radius from starting portion to ending portion, and its one end is adhered to inner bottom surface of the discharge cover 3, and the other end is adhered to rear end of the discharge valve 4.
Unexplained reference numerals 1a designates a refrigerant gas passage, 2a is a coupling hole, 3a is a flange unit, 3b is a discharge hole, 6 is a suction valve, and S1 is a compression space.
Hereinafter, operation of the discharge valve device in the conventional reciprocating compressor will be described.
When the piston 1 integrated with the armature (not shown) of the reciprocating motor (not shown) undergoes a reciprocating movement inside the cylinder 2, the refrigerant gas is sucked into the compression space S1 of the cylinder through the refrigerant gas passage 1a formed inside the piston 1, then compressed and discharged to outside passing through the discharge space S2 of the discharge cover 3.
As shown in FIG. 3A, new refrigerant gas is sucked through the refrigerant passage 1a of the piston 1 during the suction stroke of the piston 1, then the refrigerant gas pushes a suction valve 6 installed on front end of the piston 1, and sucked and compressed in the compression space S1, and after that, discharged to the discharge space S2 at a certain time.
After that, as shown in FIG. 3B, the sucked gas in the compression space S1 of the cylinder 2 is compressed by the piston during the compression and discharge strokes of the piston 1, and after that, the gas is discharged into the discharge space S2 while pushing the discharge valve 4 at a certain time. And, the compressed gas filled in the discharge space S2 is pushed by compressed gas which is newly compressed during next compression and discharge strokes of the piston 1, and then discharged out of the discharge valve assembly.
On the other hand, the valve spring 5 is pushed together with the discharge valve 4 during the discharge strokes of the piston 1 and compressed, and then makes the discharge valve 4 return by being stretched at a certain degree during the suction stroke of the piston 1.
Hereinafter, a fabrication method for the discharge valve 5 will be described as follows.
As shown in FIG. 4, the discharge valve 5 is fabricated using a die-casting method which injects an appropriate medium into a fixed first metal mold 7 and into a movable second metal mold 8 and presses.
At that time, a gate through which the medium is injected is a side gate 9 or a center gate 10 formed on side unit of the discharge valve 5. In addition, a parting line 11 which is generated after the product is molded is formed on surface on which the first metal mold 7 and the second metal mold 8 are contacted each other.
FIG. 5 is a perspective view showing the conventional discharge valve 5 formed by the above fabrication method. In FIG. 5, the reference numeral 12 designates a pressure face unit contacting with the cylinder 2, and the reference numeral 14 designates a pressure back face unit facing to the pressure face unit and closely supporting the one end of the valve spring 5.
However, there are some problems as follows in the conventional discharge valve device.
The valve spring 5 is pushed to the discharge cover 3 direction with the discharge valve 4 when the compression and discharge strokes of the piston 1 are made because the cylindrical valve spring is used, and entire parts of the valve spring 5 are compressed as closely contacted with each other, whereby a part of the valve spring 5 impacts with next part and impact noise is generated.
Also, the coupled part of the valve spring 5 and the discharge cover 3 is free end state, an eccentric force of the valve spring 5 is generated between the inner side surface of the discharge cover 3 and the valve spring 5 having flowability in moving, and therefore the movement of the discharge valve is not concentric with the axial line or a local abrasion is generated between the two members. In addition, the discharge valve is touches with inner wall surface of the discharge cover when the compression stroke is made, and therefore a noise and abrasion are generated.
In addition, the discharge valve 5 is fabricated by a press method using a metal mold, and the parting line 11 is formed on the pressure face unit 12 which contacts to the front end surface of the cylinder 2. And the parting line 11 may generates a burr, and then it is contacted to the inner side surface of the discharge cover 3 when the discharge valve 5 is operated. Therefore, a noise is generated or the movement of the discharge valve 5 is not stable.
Also, in case that the gate of metal mold is formed on side surface of the discharge valve 5, the molded product may be distorted because of flowing characteristics of the injected medium and the movement of the discharge valve is not stable because of inequality in the medium density after molding, whereby the discharge noise is made. In addition, in case that the gate is formed on the pressure face unit 14 direction, there is no machining allowance for post-fabrication, and therefore it is difficult to fabricate.